Top Mount Oil Cooler Fitment (gaskets)

[jfuerst]

I just received the top mount oil cooler mount from Sonex today and charged out to install it. After reading through the installation part of the manual and comparing it to what I have there are a few shady spots that I need to work out.

The manual has the following picture of the gasket to use:


and I have the following gaskets:


I can pretty well rule out the ones on the left as they are likely too small. But both the others seem to be workable. The middle cylinder ones seem to match the manual the best, but the quality of the photos is rather poor by the time they make it to a PDF manual. ALSO I noticed during mock-up that the included bolts for the install do not have threads long enough to tighten down the adapter all the way down flush to the engine. I am not surprised by this I guess, but the manual simply says "bolt the plate to the engine case using the hardware identified in the photo below" and I can't tell from any of the manual pictures (or any other) if the adapter plate is meant to be flush/flat against the top of the case or if there is actually a say .200" gap between the adapter and the case where the caskets are just crushed between the two surfaces. If there is supposed to be a space between I would have expected a detail like that to be mentioned in the manual. But then again the bolts don't have enough thread to bolt all the way down if that is the case.

Bolts lack thread:

Manual showing gap or no gap?

So.. Someone that has done the top mount oil plate, can you confirm if there is a gap between the adapter and the case where the gaskets are smashed or is it flush with no gap??

Assuming there is a gap, I 'm leaning towards using the flange gaskets on the right as they are the ones that would have been used with the oil cooler directly and are also the ones used to mount to the adapter. The tube ones in the middle seem more likely to leak or fold inwards pinching off oil flow.

Thanks!

[Spaceman]

Don't take my word for it because I just started building my engine the other day, but I just bolted that adapter to the top of my case as well. I'm not positive about the gaskets in your photo but I had the full gasket set that came with my engine and there were two orange cylindrical ones just like their picture, so I used those. Your middle ones look about the same but they do look a little tall I guess.

As for the gap, I agree I think they'd mention it if there was supposed to be one, and I wouldn't have much faith in those little donut seals if it wasn't clamped down all the way. I used a washer under each bolt head and two under each nut to make the supplied bolts work. I've noticed many, many (many) instances of the specified bolts in the plans being like one size too long, so I either buy the next shorter bolts if I'm feeling patient, or add a washer or two if I'm feeling impatient. I didn't think any further than that about it so now I'm curious if there's any more to it!

[XenosN42]

Hello nameless poster,

You should use the .375" thick cylindrical seals between the top of the engine case and the ACV-P01-106 mount plate.

Make sure you use the ACV-Z01-80 (button head screw). Use the washers indicated in the manual.

There will be a small gap between the ACV-P01-106 and the engine case. You want the cylindrical seals to compress by taking most of the clamping force.

Use the short (thin) flanged oil seals (the ones on the right in your photo) between the mounting plate and the oil cooler.

Context: I've used the top mounted oil cooler for five years. (The anniversary of my first flight is this May 17th!) I've never seen a leak from that area. I have removed the oil cooler each late fall and reinstalled it in mid-late spring. I do this to improve (increase) the oil temperatures in the winter. I fly out of far western New Jersey, so moderate winter temperatures.

[Area 51%]

As you are tightening the bolts that attach the cooler to the adapter plate, check for interference between the cooler bottom and the engine case. I had to file some of that boss away.

[NWade]

And a follow-on note to Michael’s informative post:
Do NOT think that you have to really crank the bolts excessively tight to put a huge clamping force on this assembly. If you overtighten these fasteners you can strip out the threads in the soft aluminum adapter plate, so just use a modest amount of torque.

Enjoy,

—Noel
Sonex #1339
AeroVee Turbo

[XenosN42]

And a follow-on note to Michael’s informative post:
Do NOT think that you have to really crank the bolts excessively tight to put a huge clamping force on this assembly. If you overtighten these fasteners you can strip out the threads in the soft aluminum adapter plate, so just use a modest amount of torque.

Enjoy,

—Noel
Sonex #1339
AeroVee Turbo

Excellent point Noel. And a note to the person with the original question: you'll need to alternate tightening each of the three fasteners to get the mounting plate to be parallel with the top of the engine case. That gives you the best seal.

[Rynoth]

I have removed the oil cooler each late fall and reinstalled it in mid-late spring. I do this to improve (increase) the oil temperatures in the winter. I fly out of far western New Jersey, so moderate winter temperatures.

That's interesting that you remove the oil cooler altogether. Do you block off the baffles as well that are related to the cooler?

This winter I applied a strip of aluminum HVAC tape across the front of the oil cooler and noticed a fairly significant rise in oil temp (20-30 degrees from before.) The cooler was probably 80% blocked by a single strip, I could have blocked it all with 2 strips but was mostly experimenting with it. The tape stayed put and left no residue when I removed it.

[XenosN42]

Hi Ryan,

When I remove the oil cooler I do block off the rectangular opening behind it in the baffling.

Why do I remove the oil cooler instead of just taping it off as you do? They have been known to fail. If it's not there it can't. Since it's not needed in the winter why not remove it? It only takes about 45 minutes. In my book the risk (blown cooler)/cost (45 minutes) analysis says remove it in the winter.

[GLENDSMITH]

I agree with your method of dealing with the top mount oil cooler. I have blown two now luckily while I was still on the ground. It really doesn't take much effort to change from with or without. I however still wish these oil coolers were more robust.

Glen
ONEX N110NX

[NWade]

After blowing my oil-cooler out I found that:
1) While the oil-pressure plunger might move freely in tests before your assemble the engine, it can very easily get stuck after the whole system has been through a couple of heat cycles and had thick oil run through it! Check that your plunger is really and truly able to freely/easily slide all the way up and all the way back down. Any kind of jam or tight-spot is going to cause excess pressure when the oil is cold.
2) I spoke to a bunch of VW gearheads online and they all went bonkers when I told them I was using 20W-50 oil. Apparently that, plus one of these style of oil-coolers, is known to be a combination that can cause blowouts in the racing world. Now I will say that our aircraft use is definitely not the same scenario as racing, and there's a lot of wisdom in having an oil that stays "stuck" to critical metal parts for longer since aircraft go through periods of disuse and that's when engine corrosion sets in. But I personally decided to step down to the 15W-40 version of the recommended oil and my pressures have been right in the sweet-spot ever since.
(NOTE, however, that my plane isn't flying. I have about 5 hours of cumulative runtime on the engine, though, as I went through a long troubleshooting process with my turbo not making full boost)

Hope this info helps,

--Noel